In recent years, high-density optical recording media of volumetric recording using holography (hereinafter, referred to as “holographic memory recording media”) and recording and reproducing devices for holographic memory recording media have been developed for practical use.
As a multiplex recording method for increasing the recording density of a holographic memory recording medium, various methods such as angle multiplex recording and shift multiplex recording have been proposed. For example, “Holographic Data Storage” by H. J. Coufal, D. Psaltis, and G. T. Sincerbox published by Springer in 2000 discloses a general multiplexing method.
In any of them, the angle multiplex recording is performed by changing the relative angle between a reference beam and a medium at a certain angle step. In the angle multiplex recording, page data of a certain size (a certain number of modulation pixels) defined by the device employed is recorded for each recording angle. As illustrated in JP-A (KOKAI) No. 2006-154163, methods of changing the angle step depending on the recording angle have been studied. However, it has not been considered to change the size or shape of page data depending on the recording angle to increase recording density.
If the size or shape of page data is changed for each recording angle, it is possible to increase the recording density in some cases. If all the pixels in page data are recorded by the same angle step as in the conventional methods, there is still room for increasing the recording density.